1. Field of the Invention
The present invention relates to a bonding apparatus such as a wire bonding apparatus, die bonding apparatus or tape bonding apparatus and more particularly to a bonding apparatus that includes a means which takes images of a workpiece to be bonded.
2. Prior Art
A bonding apparatus is generally equipped with a heating block which heats the semiconductor workpieces and a bonding tool which performs bonding on the semiconductor workpieces along with a camera and an optical path housing which are used to obtain the images of the semiconductor workpieces.
In order to perform high precision bonding with such a bonding apparatus, it is necessary to specifically recognize the positions of the semiconductor workpieces. Meanwhile, in order to shorten the time which the bonding tool takes to move to perform bonding, it is necessary to shorten the distance between the bonding point for each semiconductor workpiece and the recognition point where the semiconductor workpiece is recognized.
Accordingly, the bonding tool and the optical path housing are installed in close proximity to each other. However, this means that the optical path housing is installed in close proximity to the semiconductor workpiece. As a result, the optical path housing is in an environment of radiant heat or a high-temperature atmosphere, etc. generated in the vicinity of the semiconductor workpiece, which is heated to a high temperature by the heating block.
Since the camera is generally designed so as to work at room temperatures, when the optical path housing is exposed to such a heated environment, thermal expansion occurs therein, and a positional deviation tends to occur in the optical path housing during the object recognition or image obtaining process.
One example of a conventional means for preventing thermal expansion of the optical path housing is to blow cooling air onto the optical path housing, and this is disclosed in Japanese Patent Application Laid-open (Kokai) No. H7-147297.
Generally, the optical path housing, which is connected to the camera, is installed on an XY table, and it may be positioned above the heating block during the process of recognizing the semiconductor workpiece. On the other hand, the optical path housing may be positioned away from the heating block when the type of workpiece to be handled is changed.
Accordingly, in the prior art described above, periodic or irregular heat changes inevitably occur in the optical path housing as a result of repeated heating, which is when the optical path housing is moved near the heat source, and as a result of cooling, which when the optical path housing is moved away from the heat source and when cooling air is blown thereon. As a result, an unexpected positional shift in the recognition position occurs due to the deformation of the optical path housing. In addition, deterioration in the parts of the optical path housing progresses rapidly. Furthermore, even if cooled by the cooling air, if automatic operation is initiated while the optical path housing is at room temperature, thermal expansion of the optical path housing gradually proceeds, so that the recognition results obtained after several hours of automatic operation differ from those obtained immediately after the initiation of automatic operation.